In ABS systems, it is known to connect the solenoid coils of the solenoid valves to electronic control circuitry remote from the coils by way of a conductive card (2), as shown in FIG. 1. The electronic control circuitry (not shown) is not located in the housing (4) since the circuitry can be damaged by the ambient conditions such as temperature, vibration and moisture.
The conductive card (2) is mounted in a housing (4), which also contains an array of electric solenoids (8) (only one of which is shown). Housing (4) is mounted on a valve block (10) which is of ferromagnetic material and which conducts the magnetic flux developed by solenoid coils (8). The valve block (10) comprises a plurality of domes (11) (only one of which is shown) containing mechanical switch parts (12) of the solenoid valves. Each coil (8) is annular and surrounds a respective one of the domes (11). It is important that the coil (8) is aligned accurately with respect to the dome (11) in order to obtain optimum magnetic flux. The solenoid coil (8) is coupled to conductive card (2) through holes (3) in the conductive card (2) via two stiff wire leads (14). Thus, it is important that the wire leads (14) are accurately aligned with the holes (3). Such a need for accurate alignment increases the difficulty of attaching the solenoids via the leads (14) to the conductive card (2) and increases the production costs. Furthermore, it is necessary to accurately align the solenoids (8) relative to the switch parts in blocks (10) which also increases the production costs.
To assemble this arrangement, electrical connections must be made between the control circuitry (not shown) and the conductive card (2) and between the conductive card and the solenoid coils (8)
This arrangement suffers from a number of additional disadvantages and problems due to the necessitated separation of the control circuitry and solenoid valves. For instance, a significant amount of space is required for the solenoid valves and the control circuitry, additional electrical connections must be made during assembly, the conductive card and the leads (14) can be damaged during assembly, and the conductive card may be subject to corrosion particular since the connection of the housing (4) to the valve block (10) does not provide a sufficient seal to protect the card (2) from ambient conditions.